After a part using a time signature continuing without any time signature

When starting a new flow without any time signature no bars appear, it’s a free measure.
I start a flow with that free measure. Then comes a part (within the same flow) where I need i.e. a 4/4 time signature. I set it and use it for a while. When this 4/4-part ends, is there a way to return to that former time-signature-free state (within the same flow)? I found no way to delete a time-signature and replace it with ‘nothing’.
Thanks for any advice / support!

To go back to free measures, type Shift-M open Enter, or Shift-M x Enter. Typing open will display no warning whatsoever on the page (but will give a non-printing red signpost to tell you that the time signature is there) and typing x will give an x time signature on the page. Having inputted either of these, you’ll find an Open style property in the lower zone that allows you to switch the visual representation from an x to nothing or the Penderecki symbol:

Thank you very much, that was exactly what I was searching for. (and yes, I should have found that in the manual actually …)