Example file structure:
xxx.psd -> 1.kra -> 2.kra

Currently Krita supports file layers and when nested file contains file layer such layer is loaded nicely. But when 1.kra is changed e.g. filter layer is added or when xx.psd file inside 1.kra is relocated to something else like yyy.psd using new path option feature from 4.0 then Krita says that can't find source file when opening 2.kra

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The file associated to a file layer with the name "Layer 2" is not found.

Expected path:
D:/temp/xxx.psd

Do you want to locate it manually?
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I'm not sure if it's limitation or bug, but maybe such report will be useful.