In the software setup interface or software installation interface, add a memory size setting option.
just like SweetHome3D.l4j.ini

Maybe in a future version...

The default use of 0.9G in software 32 is very small, and the 64 bit 4G is too small.

In 32 bit, a higher value won't work. In 64 bit, the default max is half of the available RAM.

Is max mem 14.2 Gb?

When run in 64 bit, the working limit must be the RAM size available on your computer when Sweet Home 3D runs.