Every transmission guy I talked to when I had my shifting Blockers / Brass Syncros replaced told me to try to never rest your arm / hand or pull on the shifter other than the task of shifting itself.
The gears and blockers will last longer with a "natural" load against them (which is no load).
If you watch the shifter while driving it moves quite a bit when going over bumps and rough roads.
It even vibrates on the pavement at times.
Placing unnecessary weight on the shifter during its "natural" movement is placing stress on the Blockers / Brass Syncros.
I trust their opinion rather that assuming, because the shifter is never totally still while in motion down a road.
Common sense would tell me that no weight is best,.... but you must have a shifter so..................... the lighter the better.
BTW I had to replace my stuff because of "forced speed shifting" ................... doing the spirited driving stuff when younger
Its best to press the clutch completely to the floor when shifting and never rest your foot weight on the pedal of hand weight on the shifter when you are not using them.
But that's only important If you want them to last and stay smooth during their natural wear lifetime.
AND don't hold the clutch in at red lights or while idling for extended time,... use neutral it will save wear on the pressure plate and throw-out bearing and other parts in the system,... life lessons can get expensive.