How are you creating your Booklet?
Try this method which doesn’t change margins. I’m using Pub 2016 which I’m sure will be the same as 2019 in respect to the options shown.

Open Publisher with say an A4 portrait page.
Click the Page Design tab, then Page Setup.
Open the Layout type options and opt for Bookfold.
Now change the Page width/height values to W21cm and H29.7cm > Enter key.
Accept the Automatically insert pages.

Add content to page 1.
Add content to page 2 & page 3.
Insert your image/picture/circle while on pages 2&3 and align as reqd (central vert/hori?).
Add content to page 4.
Check the print preview (should show no margin down middle of inserted image/picture/circle).
Print first side (page 4-1), let the page dry, then turn over and insert back into the tray in the correct orientation and print on the blank side which will be pages 2-3.
Note: In my example below, I have printed to PDF (2 pages) and not used a physical printer.
A non duplex/print both sides printer will show the user a dialog print box advising on printing both sides of the same sheet.

Hopefully, no margin/white strip will show in the inserted item which is across pages.
Click the image below to see how I have done the above and I hope it helps you out.