Is it permissible to have the dua of entering toilet on the door of the bathroom

It is permissible to display Adhkar for the purpose of remembrance, but they should be placed in a suitable location, to preserve their dignity and prevent disrespect. For example, the Dhikr for entering the washroom should not be placed on the bathroom door, but rather on the side of the door from the outside, to the right or left of the person entering.

Sheikh Ibn Baz (may Allah have mercy on him) was asked:

"Is it correct to place verses or reminders Adhkar from the Prophet (peace and blessings be upon him) on the walls in rooms for the purpose of remembering Allah the Almighty and for contemplation? Please guide us, may Allah reward you with good."

He replied: "The correct view is that there is no harm; if it is for the purpose of remembrance, placing verses on the wall, or hadiths for remembrance, there is nothing wrong with that, if it is for the purpose of remembrance and benefit, like hadiths about greeting (salam), supplication (du`a), hadiths about forbidding what Allah has forbidden, or encouraging obedience to Allah, or verses; there is no harm in that in a gathering or in an office," End quote from the website of Shaykh Ibn Baz.

And Sheikh Ibn `Uthaymeen (may Allah have mercy on him) says: "As for - writing hadiths - in the house: there is nothing wrong with writing a hadith that has a benefit, like the expiation of the gathering: (Subhanaka Allahumma Rabbana wa bihamdika, ash-hadu an la ilaha illa ant, astaghfiruka wa atubu ilayk) this contains a reminder," Eng quote from "Liqa' Al-Bab Al-Maftuh" (197 / 13).

And Allah knows best.