The description of the Glyph of Warding spell states, in part (emphasis mine):
When you cast this spell, you inscribe a glyph that later unleashes a magical effect. You inscribe it either on a surface (such as a table or a section of floor or wall) or within an object that can be closed (such as a book, a scroll, or a treasure chest) to conceal the glyph. The glyph can cover an area no larger than 10 feet in diameter. If the surface or object is moved more than 10 feet from where you cast this spell, the glyph is broken, and the spell ends without being triggered.
The description of the Portable Hole magic item states, in part (emphasis mine):
You can use an action to unfold a portable hole and place it on or against a solid surface, whereupon the portable hole creates an extradimensional hole 10 feet deep. The cylindrical space within the hole exists on a different plane, so it can't be used to create open passages. Any creature inside an open portable hole can exit the hole by climbing out of it.
Say I climb into the Portable Hole, cast Glyph of Warding, climb out, and fold up the Portable Hole.
Can I then travel around with the Portable Hole, and still have the glyph function when I retrieve it out of the hole?
Alternately, can I jump into the Portable Hole and activate the glyph myself for a buff?
Best Answer
I would rule that the glyph would still function, as long as you jump into the hole, for the following reasons:
As written, the portable hole creates a space that exists on a different plane. What this means is that the hole is effectively a portal to another plane. In this case all that has moved is the entrance to the plane, and not the plane itself. Given this, the glyph hasn’t moved at all.
This is an inventive use of a spell and a magical item and as such the player should be rewarded.
If following the ruling it turned out that it was too powerful, or that it was in some way breaking the game, it is easy enough to put a stop to as a DM.
As an example, after a few times of you disappearing into this hole and coming out super buffed, your enemies are going to have heard about your tactics in advance and as soon as you jump in, they will move hell and earth to get to the hole and fold it up with you still inside!
TL;DR
There is no reason that this wouldn’t work. You are placing the glyph on another plane of existence and then moving the entrance to the plane.
Based on a comment from @David Coffron (thank you!), I would add that removing the item that the glyph is cast on is a different matter. In removing the surface on which it the glyph is cast from the hole the glyph would be moved more than 10 feet. The spell specifically says
I suspect that this is to stop players casting it on an object and then teleporting.