I have read through the recent “multiple time signatures” post and understand the solution to the problem there but am having a related problem inputting the opening bars of Act 1, scene 3 of Debussy’s opera, Pelléas et Mélisande (attached). In particular, I haven’t found a way to show a different time signature for only the oboe for the very first four bars. Using hidden tuplets I am able to show the oboe notation absent its unique time signature but haven’t found a way to make both its time signature and the more widespread one visible at the same time right at the first bar. I suspect this would only be possible if there was a way to enter something on the oboe stave that looks like a time signature but doesn’t behave like one but wonder if I might be missing something.
You have to input these special bars - each of them - as „longer than normall“ ones. You do this by writing this into the popover:
c,6
(and if course making it local with alt/option-Enter)
This is understood by the program to create a 4/4 measure with „pickup“ length 6 (quarters) which amounts to 12 eights. This way the measure have the same length as the surrounding 12/8 measures. Since this only works for one bar at the time, you have to repeat the procedure for every one of these „overstuffed“ bars. Then you have to use (hidden) tuplets to get quarters for dotted quarters etc. (as you did already)
[Personal note: being German speaking, where we have just „Takt“, I‘m never sure where to use „bar“ vs. „measure“ - maybe some native speaker can enlighten me about this? Or is this just another American/British English differentiation?]
Addendum:
the reverse case - making a bar shorter than its official length declared by it’s time signature - can be accomplished in just the same way: write the definition of the time signature, followed by a comma and then the real length calculated as (decimal) number of beats. So for creating a single 12/8 time signature bar in 4/4 length that would be 12/8, 8. This is - if course - how pickups are created normally. It‘s just redefining the real length of the one bar at hand.
Alternatively you can shorten every measure independently from its time signature by just inserting a bar line where you want one - nothing will explode 
British vs American, that’s all. Bar is British.
In (my experience of ) common practice in the U.S., the two are largely interchangeable. But…
Some nuance:
“Bar” is used exclusively for notational elements like barline and bar rest (though people sometimes say things like “the oboe has a full measure of rest”). However, one funny quirk: I hear “bar 30” or “measure 30” to identify a spot in a piece, but the abstract element itself is more often (in my experience) called a “measure number” (as in, “I want my measure numbers italicized”).
“Bar” is quicker to say in rehearsal, so it’s used a lot. In academic music theory writing, “measure” is generally used.
And at the end of the day, I’m much happier finding myself in a bar for good measure than the other way around.
I appreciate how (ahem) “Takt-ful” you are in asking this, Michael. 
But… Shakespeare wrote Measure for measure… 
Many thanks—worked like a charm.
Well said!
Judd, thanks for the thorough explanation - I‘m always into nuances 
If I’m not mistaken, „Takt“ can also sometimes translate to “beat” in English.
You use Takt in Swedish.
Jesper
I would be surprised … do you mean this in the sense of tactus?
I may have misinterpreted notes in Mahler, etc., but I thought e.g. „ohne Rücksicht auf dem Takt“ refers to the conductor’s beat, or possibly the note value, such as quarter or half.
Ah! This means independent from the beats as beaten - it’s a bit sloppy formulated but clear for the German reader. Indeed it means in relation to the meter, somehow pars pro toto, or the other way round …
Ja, I was just thinking … I guess, if you take the original meaning of tactus, to touch something regularly to keep time, we can indeed say it’s synonymous with the beat.
So in German we would say:
“Wir spielen noch einmal von Takt 17” {measure}
“Kannst du nicht im Takt spielen?!” {keeping time}
" Dave Brubecks ‘Take Five’ steht im Fünf-Viertel-Takt." {meter}
I never thought about this consciously …
EDIT: added third example phrase
Another one:
Four- stroke engine ……… Viertaktmotor
Am I correct that one meaning of vertakten is “segmenting”? If so, that makes a ton of sense: musical time is segmented at the larger pulse-level of the measure, then to the smaller beat-level pulse.
I’m not sure I have ever used “vertakten” … I would maybe scratch my head – but it may be a word in some contexts.
Yes, it is heavily offtopic now, but maybe musicians language is interesting still.
German …
Composer to engraver:
“Takt 31: die Pause auf dem zweiten Schlag muss eine Achtelpause sein und eine Achtelnote f muss dort ergänzt werden. Außerdem fehlen noch die Akzente auf dem ersten Schlag und jeweils auf der Achtel nach dem dritten und fünften Schlag. Die vier Achtel(noten) auf Schlag vier und fünf müssen g statt f sein.”
Musicians rehearsing:
“Wir müssen im Takt 31 die Akzente auf 1, 3 und und 5 und noch besser herausbringen!”
The last thing comes from counting quarters and eighths, especially in music lessons for children:
“Eins-und-zwei-und-drei-und-vier-und-fünf-und! Immer schön im Takt bleiben!” (although it’s still 23% of the real tempo 
)
Lots of idiosyncrasies… But the more I think about this the more I think @Mark_Johnson is right, and Takt probably originally was a word for beat. The usage of Takt for the whole measure seems to be pars pro toto. We have no separate functional word for measure. I think I will research how this came about.
(I have no idea where the meaning of Takt for tactfulness comes from, but this is at least the same word root as in English obviously.)