I noticed that in my digital planer I can insert images by simply dragging and dropping them from the gallery. I can’t do that in Krita.
Hello @skanikart and welcome to the forum 
What do you mean by that?
Which gallery is this?
Do you mean any image on any website or is it a particular website?
Do you mean that you can do that in other painting apps on android?
I don’t use any painting apps on android so I can’t give advice about this.
There are people on the forum who do use krita on android so please wait to see if any of them come along to give some help.
Edit:Add: Changed in response to your change about “digital planer”
Omg, sorry. I’m using a translator. I meant Penly planner. In general, I meant that on a computer I can move an image from a website to krita with the mouse by simply dragging it, but on android it doesn’t work.
The Penly Planner is an android app. There may be app data isolation aspects of android that prevent you from doing that.
The android file system and security/permissions behaviour is known for preventing easy data transfer 
Please wait for someone who knows more about krita on android to give advice.
Yes, Penly has managed to do that, so I can drag and drop images there. But it doesn’t work in Krita, maybe someone can fix it(
Yeah, with drag & drop the target app only receives the file name of the image, and then has to be able to access the file location.
This subject area was mention in July 2023 here:
Images copied from other applications cannot be pasted directly into Krita
The problem is known to the developers.
As I understand the situation, there is now a shortage of android developers for krita