Is there a way to add a project button in Zremesher like it haves in Dynamesh, using the Zscript?
Not really. You couldn’t literally add a button to the same part of the Tool palette. But also, ZRemesher doesn’t work in the same way as Dynamesh. ZRemesher is a mid to low resolution topology solution. If you want details projected then you can use the Freeze Subdivisions button. Alternatively you would duplicate the subtool, zremesh the low res of one, then subdivide and project the high res from the duplicate. You could script that but it is probably better that the user has full control.