This is where you focus your aim at the left grip assembly. Find the clutch lever's little arm that pushes the safety switch in if in gear and all that. Then listen to the engine shift while watching the arm move in and out and never really is pulled all the way in for shifts.
The clutch lever presses a safety switch so that bike can be started in gear ONLY if the clutch is pulled.
I don't think that could have any impact on shifting gears but the clutch master cylinder push rod could. If the lever is not pressing that push rod in far enough, the clutch is not fully disengaging.
Is that rod worn or bent? Is the lever worn or has it been modified? Is the lever pivot worn? I presume you have tried adjusting the lever to maximum throw although the clutch should fully disengage even if it is set at minimum throw.
I would think the bike would be creeping forward with the clutch pulled if the clutch is not fully disengaging. This should not happen when the bike is thoroughly warmed up.
'08 MIDNIGHT SAPPHIRE BLUE Now Deceased