you will find in the toolbar category < Meter>. The button (Icon) "Insert bar(s)" you will find in the toolbar category < Meter>.
Click into the bar, behind which a new bar or several bars should be inserted. Afterwards, click on the button (Icon) "Insert bar(s)"
TIP: With a click with the right mouse-button into the corresponding bar, you can open a submenu, that also contains the function "Insert bar(s)"
You can also find the function "Insert bar(s)" after a click with the right mouse-button into the corresponding bar. The submenu following on it offers the function"Insert bar(s)".
A dialogue appears and you will be asked for the amount of bars which you intend to insert.
The bars are inserted in all voices in accordance with the last time signature.