Can I make the space bar act as left click in Altium?
Keyboard and Mouse function tables exist in the registry to be shared for all common windows functions.  Each application can have custom local and global mappings so that only that program uses those undefined elsewhere combo-keystrokes.

However to use a common Windows, global key for just Altium requires that HKCU\Software\Altium has a  Policy change or a temporary change in the registry just when Altium is running.  ( details for others to suggest takes time)

Alternatively , one can add a second mouse with an good foot switch or bar wired to the left mouse and use that instead of pointer finger or peddles and exercise those feet. (lol)