How to set the same user defined text in multiple places in an Impress presentation?

I would like to have the name of a client automatically set in multiple places in a presentation, mainly on multiple master slides, and only have to set it once. Is there any way to achieve this in Impress?

Am I correct in understanding that you cannot create custom user variables for use in Impress presentations? This would seem like the solution, but the option described in e.g. the writer documentation, i.e.

Insert - Field - More Fields - Variables

isn’t there in the Impress menu.

For my project, I’ve insertet a rectangle with some text with a macro in my master. May be an idea