You can designate as many sanctuaries as there are places strongly linked to your deity (that you have visited in)
Word of Recall has two parts:
- The method by which you designate a sanctuary
- The translocation back to one of your previously designated sanctuary
How do you designate a sanctuary?
Word of Recall states:
You must designate a sanctuary by casting this spell within a location, such as a temple, dedicated to or strongly linked to your deity. If you attempt to cast the spell in this manner in an area that isn't dedicated to your deity, the spell has no effect.
So to designate a sanctuary it must be:
- A location you have visited, specifically one in which you have cast this spell
- Dedicated or strongly linked to your deity
The spell places no limits on the number of designated sanctuaries, nor does it say if you designate a second (or subsequent) place as a sanctuary that the dedication of the first location is broken.
The act of designating a place as a sanctuary, using this spell, makes it forever a sanctuary for you.
If you have multiple sanctuaries, can you choose which one to go to upon subsequent castings of this spell?
Word of Recall states:
You and up to five willing creatures within 5 feet of you instantly teleport to a previously designated sanctuary. You and any creatures that teleport with you appear in the nearest unoccupied space to the spot you designated when you prepared your sanctuary (see below). If you cast this spell without first preparing a sanctuary, the spell has no effect.
As you noted it specifies a previously dedicated sanctuary, not the previously dedicated sanctuary. It, however, leaves silent the method of choosing which of the previously designated sanctuaries you are teleported to.
Since the wording of the spell does not explicitly impart an explicit choice, it's up to DM discretion which sanctuary you arrive at. The DM has a few potential options:
- The nearest sanctuary (however this has the drawback of making the spell useless if you cast it in a place that is one of your designated sanctuaries)
- The nearest sanctuary that the character casting the spell is not in
- A randomly determined sanctuary
- Allow the character/player to choose
- DM chooses an appropriate sanctuary at their discretion
Out of these options, the first clearly goes against the intention of the spell in the case where the characters are in a previously dedicated sanctuary (in this DMs opinion) and should be ruled out, as in the edge case it would not actually provide sanctuary for the character.
Among the other options, this DM would allow the characters to choose. If they have been well travelled enough to setup numerous sanctuaries, remebering that the sanctuaries have to be somewhere specifically dedicated or strongly linked to your deity (eg a temple), then they should be rewarded for that pre-planning and effort.