Kindly refer to the following link(s):
https://www.assimalhakeem.net/i-have-a-friend-and-he-always-when-he-said-i-will-do-this-inshallahhe-add-inshallah-taala-i-never-hear-him-to-use-just-inshallah-is-this-kind-of-bidah/
Ruling on saying inshaAllah
Prohibition of saying 'in sha Allah' while making Dua!
Saying in sha Allah while making an oath
When should we say in sha Allah? (used with things in the future)