It means if you want to put it that way. A speaker adds it to flag that a word is a chosen or loose description. So to speak is a close equivalent. A new job might make you a gatekeeper, if you will, approving every request.
It is not a prediction. In It will rain the speaker forecasts the future; in if you will nothing is expected to happen, it only qualifies the wording.
- A coach telling the team, We are rebuilding, if you will, from the ground up. The coach knows rebuilding is one way to frame the situation, and other people might describe it differently.
Not a prediction about the future
The confusion to avoid is reading if you will as a normal conditional with the modal will. In If you will follow me, I will show you the office, will really does point to the future, and the sentence sets a condition.
The set phrase works differently. Nothing has to happen for it to be true. In He is my right hand, if you will, the speaker is only offering a chosen way of wording things, not predicting anything or setting terms.
So when if you will sits inside a sentence, set off by commas and qualifying a word, treat it as a fixed expression. When it starts a full clause about what someone might do, it is the ordinary conditional use.