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I would say, that it depends on if it should be tightly integrated with an aircraft (as a mod) or if it is a more general tool used over several aircrafts.
In the latter case I would probably suggest making a new toolbar panel in JS (see https://github.com/bymaximus/msfs2020-toolbar-window-template).
If you need more advanced SimConnect functionality, like masking events, you might opt for WASM.
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