I'm not sure the best way to accomplish it, but it would be nice to incorporate some sort of option list for rolls. Let me explain:
I'm playing a Pathfinder campaign as a Dwarf Barbarian. Because of various feats and abilities, there is rarely a time I have a simple "attack" roll -- there are modifiers if I'm using a one- or two-handed weapon, each of which has its own modifiers, whether I'm using a Power Attack, whether I'm in a rage, whether it's my first or second attack, whether it's the first hit in a round, plus natural attacks like bites and horns, and whether THOSE are a primary or secondary attack, along with Critical confirmations, damage rolls, damage from critical...
As a result, I have dozens of macros, reduced to just a few characters each for the names, and they fill my macro bar. Just for attacks. Trying to remember which macro is which when they are not in the bar takes almost as long as trying to locate all the modifiers on a character sheet and type them in each time.
There are a number of ideas I've had. Conditionals would help - especially on things like crit confirmation. Having a checklist where I could tick off "Attack: 1st; Weapon: +2 Greatsword; Rage: True; Power Attack: False; Vital Strike: True; Lunge: False" and so on, and let it caclulate all the associated values. Giving macros a separate Display Name and identifier (so one could type #rpa but see "Raging Power Attack" on the list). Or perhaps Drop-down lists -- so I could select "Attack" on the macro bar, and then select from a list of various macros involving different attacks.
Character Variables would be wonderful too -- every time I level up, I have to go through and update EVERY macro again, and hope I didn't miss one... I've tried breaking it up so that, in a macro, I may have /roll 1d20+(3+3+2)+2-2+1 just to help remind myself which bonuses and penalties are coming from where. Being able to have -- while not a FULL character sheet in roll20 (though I suspect no one would complain if there was) -- at least some way of entering a few key values that the macros could refer to -- allowing us to update in one place (when leveling up or obtaining a new piece of stat-altering equipment) and have the corresponding macros all use the new value.
I'm sure some of the suggestions here have value in many other systems, not just Pathfinder, and I'm not sure which ones would be the most effective, but hopefully it helps a bit. Thanks!