It has always been easy to change file associations or file types. But this type, Microsoft had made a mess with regards to some third-party apps with the latest Windows 10 update.
The folks at Howtogeek tested this theory and found out that Microsoft doesn’t allow certain apps to be set as default for certain file types.
They ran tests and this is what they found out. Some apps like Photoshop and Notepad++ cannot be set as default apps in Windows 10 for some unknown reason. Only a few apps worked like VLC to be set as default for video files. This issue exists on the April update but was later on fixed on the October 2018 botched update which was later pulled out due to data loss that were reported by users.
October 2018 update is still pending its re-release and as of this writing, Microsoft has not released a final stable version or statement when the company plans to release the said update once more. Until the latest build release is rolled out, users might still encounter this bug that affects April 2018 update users.