Removing any automatic calculation for GST Amendment is currently unavailable in QuickBooks Online. When a GST adjustment was entered in QuickBooks, it automatically adds a general journal entry to show the adjustment. Therefore, any adjustment made will be included in the next time you lodge your GST.
If you have lodged your BAS already, any changes you have made to that period since the lodgement will automatically appear as amendments/adjustments to that BAS. You can see these in a list in the GST Amendment Report under the Reports section.