This feature request was discussed with Campbell Barton during meeting 2021-02-23
Currently it is not possible to apply modifiers to an object that has shapekeys, even though it would be technically possible for most modifiers. I suggest making it possible to apply modifiers to objects with shapekeys with some exceptions.
The subdivision and wire modifier does not modify the objects topology as the shape change. This modifier could be applied while still keeping the shape keys.
Screen capture example of how to apply modifiers and keep shapekeys.
Modifiers that can't be applied in a simple way when the object has shapekeys.
- Geometry nodes (in some cases. Easiest to just exclude this modifier)
- Mirror (IF USING BISECT)
- Volume to mesh
- Particle instance (Since source particle system density mapping can be applied in world space)
- Particle system
When the user tries to apply any of these modifiers when the object has shape keys, the error message should be:
Modifier that changes topology based on shape cannot be applied to a mesh with shape keys
When applying a modifer of type "Modify" (for example "Data transfer"), the current shape should be used when applying the modifier (i.e. the resulting shape of all combination and values of the objects shape keys)