So, this breaks down into (a) edit rights for various trust-levels in general, and (b) what you can do with polls, and how these two intersect.
In general, you get more edit rights as you spend time in the forum (you can see this post for a high level overview and this post for all the detailed defaults). As SC members, we regard you as trusted members of the community, so you’ve already been set to TL3, which grants you power over recategorising, retagging, & renaming topics, as well as making wikis, and more. And TL1+ can always edit their own posts.
Potentially I could see an argument for SC members to be TL4 (which has no automatic promotion, it has to be given), or even made forum moderators - that’s a debate we need to have, along with other highly-active people. Either of those would grant you the power to edit post bodies from other people, which may be required - or if it’s infrequent, perhaps just using the Flag button to ask staff for help could work too.
That’s editing in general. However most of this doesn’t apply to polls - even as an admin, I can’t edit a poll once it’s more than 5 minutes old (that can be altered, but I approve of the idea in general, so I wouldn’t want to set it to something huge). That’s because changing a poll usually invalidates the existing votes, so Discourse enforces it. As such, none of us can edit an existing poll, we can only make new ones.
One exception to this is the CloseAt property, which auto-closes a poll. That also cannot be changed after the 5min grace period, and once the poll closes it cannot be re-opened. Contrast that to an open-ended poll, which is closed manually but can then be re-opened if needed.
So the question I would ask back is “what sort of edits are you doing on GitHub?” and also perhaps “how often do you find that needed?”
If it’s around clarifying options, improving wording, etc, then we can replicate that - the body of the post can still be edited to add notes, especially if subsequent discussion reveals a misunderstanding in the vote. But if it’s changing a poll-in-progress, then those will need to be closed and restarted. The one gray area is on auto-close, since that can’t be edited later but manual-close is … well, manual.