Yes, mostly. Only three fields are locked so the offer keeps matching what your guest was promised, and you can still change everything else, including the discount.
The three fields that are locked
When a coupon is connected to an automated campaign, a banner at the top of the coupon says "This coupon is connected to an automated campaign. Certain fields are uneditable to maintain consistency with the campaign." These three fields are greyed out, so you can tell at a glance which ones are locked:
The coupon code
The start date
The end date
This only applies to coupons connected to an automated campaign. You can edit any other coupon as usual.
What you can still edit
You can change all of these on a campaign coupon:
The discount, both the type (percentage, fixed amount, or free delivery) and the amount
The description, which is the line guests see with the coupon code on your menu
The coupon's name
What the coupon applies to, and the minimum spend
Usage limits
Redeemable channels and order types
⚠️ Think before you change the discount, Applied To, or Minimum spend. The campaign email or text already told your guest what the offer is, so changing these can leave the coupon out of step with the message they received.
Stop an offer you no longer want to run
⚠️ Do not edit the coupon to stop promoting an offer. Use one of these options in your Owner Dashboard instead.
Pause one campaign: Go to Marketing › Automated, open the campaign, and pause sending. Offers already sent can still be redeemed.
Turn off all automated marketing: Go to Settings › Marketing and turn off Automated marketing campaigns.
Stop redemptions right away: Go to Marketing › Coupons and turn off the coupon's Available toggle. Owner warns you first that disabling the coupon will make it invalid and may also turn off the campaign, and you can cancel at that point.
Disabling the coupon is the strongest option. If you only want the campaign to stop sending, pause the campaign instead.