For lack of a better name, there are a number of things which won't be added as features, or won't be fixed. You can ask for these, but your request may be closed as wontfix without further comment. This list may be added to over time.
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Support for token art: This application is intentionally lightweight, so won't have token art. If you'd like something that looks more visually-appealing (and possibly has token art), check out https://www.mtgtokens.app
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"Complex behaviour": This is a basket of use-cases which are too niche, or which would require disproportionate effort to address in the app (and would likely sacrifice a pleasant UX for other users). Things that come to mind: buttons for "add a token with one more +1/+1 counter than this one" or "create this token but with 1 more power and toughness"