Ruling on putting books on top of the Mushaf
Question

What is the ruling on putting books on top of the Mushaf?
Praise be to Allah.The scholars are unanimously agreed that it is obligatory to protect and respect the Mushaf, and it is prohibited to expose it to mistreatment and mishandling. Undoubtedly respecting and venerating the Mushaf comes under the heading of venerating the symbols of Allah. Allah, may He be exalted, says (interpretation of the meaning):
{That [is so]. And whoever honors the symbols of Allah - indeed, it is from the piety of hearts} [al-Hajj 22:32].
Secondly:
There is nothing wrong with putting one Mushaf on top of another. Ibn Hajar al-Haytami (may Allah have mercy on him) said:
It is permissible to put one Mushaf on top of another.
End quote from al-Fatawa al-Hadithiyyah (p. 164).
As for putting another book – or books – other than the Mushaf on top of the Mushaf, that is not allowed, and the least that may be said concerning it is that it is disliked (makruh).
Al-Hakim at-Tirmidhi (may Allah have mercy on him) said:
Part of respecting it – meaning the Mushaf – if it is put down, is not leaving it open, and not putting any other books on top of it, so that it will always be on top of other books.
Al-Bayhaqi (may Allah have mercy on him) said, discussing the etiquette to be observed with the Book of Allah:
… No other book, no garment nor anything else should be placed on top of the Mushaf, unless there are two Mushafs, one of which is placed on top of the other; that is permissible."(Shu‘ab al-Iman  3/329).
See also: al-Fatawa al-Hadithiyyah (p. 164).
Shaykh ‘Abd al-Karim al-Khudayr (may Allah preserve him) was asked:
What is the ruling on putting books on top of the Mushaf?
He replied:
The Qur’an is the word of Allah – this applies to what is between the covers of the Mushaf – and the word of Allah must be respected. It is not permissible to show disrespect to it under any circumstances, and the one who shows disrespect to the Qur’an is in grave danger, because he has shown disrespect to the One Who spoke these words, namely Allah, may He be glorified and exalted.
If putting other books on top of the Mushaf was done unintentionally, then the one who forgets or does something by mistake is pardoned.
If it was done out of ignorance, the one who is ignorant is also excused.
But if it was done knowingly and deliberately, that is not permitted, because it is a type of disrespect."(Sharh ‘Umdat al-Ahkam 35/17).
If it appears to be the case, based on the nature of what is placed on top of the Mushaf, that that things was put there to protect it, and the Mushaf is a means of protecting it, or the thing that is placed on top of the Mushaf is something that is usually treated with disrespect, then undoubtedly that is prohibited, because in both of these cases, and similar cases, it is clearly disrespect towards the Book of Allah, and that is undoubtedly haram.
For more information, please see the answers to questions no. 95753 and 125930 .
And Allah knows best.