Hrm. So I couldn't figure out how to do it from KDE directly, but mounting it manually seems to work fine. Ex:
mkdir smb-mount
sudo mount.smb3 //myserver/myshare smb-mount -o user=myusername,uid=1000,gid=1000
Even without specifying "exec" it seems to work out of the box. No changes required to any configurations or anything.