How to write anticipated chords and control staves length?

Here is an approach which might meet your needs, or might not! No guarantees given.

In Write mode, enter some notes in a second voice (eg Down-stem Voice 1). The notes should be the shortest duration that will exist in the piece, or at least in each system. For example, if the shortest notes will be 8th notes, then fill one bar with those. Select them, and maybe move them down an octave or so (out of the way for when you enter the notes which you want to see). Open the Properties panel and under Common > Color, change their Opacity to 0%. While they are still selected, in Engrave mode > Properties > Notes and Rests, enable Hide stem and Hide ledger lines. Go back into Write mode. Select the whole bar and press R to repeat into the following bar, and the next, and so on. Then enter the notes which you actually want to see into another voice (eg Up-stem voice 1).

You might find it easier to leave the hiding of the notes in the second voice until later on and select them by using Edit > Filter > Voices > whichever voice you chose. You might also want to enter the “real” notes before entering the second voice and hiding it.

The spacing between barlines should now be equal. One big downside is that you might have to choose quite a small staff size to make things fit. A lesser downside is that you will probably have to flip stem directions in the visible voice because there is a second voice on the staff, even though it has been hidden. A third issue could be that this method might only be usable for systems of 4 bars, unless the shortest note value is reasonably long.