Plan groups must stay "pure": all Preset or all Custom. On the subscription page a group with Preset plans shows a portion selector; if a Custom plan sat in the same group, customers would still be asked to pick a portion even though the Custom plan already fixes the portions per category. The Group dropdown therefore hides incompatible groups, and if the plan's current group is incompatible the warning appears so you can move it. Create a separate group (for example "Chef's Choice Portions") for your Custom plans.