Archicad 18 will automatically install in a separate folder.
All versions of Archicad do.
The only thing is, because you have installed 18 last, you may find that double clicking a PLN to open it will try to open in 18 by default.
But that can be changed so 26 becomes the default again.
I don't now anything about Architerra.
Is it an add-on that only works in that version (18) or can it just be installed and will work in 26?
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
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