There is a 'relative construction' tool that will allow you to place an object or start drawing an element halfway along the distance you choose.
I am not sure of the tools name, I just call it the halfway tool.
I am not sure if it is in a standard menu or toolbar, as I have a custom setup I have used for years.
But you will find it in the 'Control Box' palette.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10