In the library object, select a frame that can be resized for the text fitting purposes, and then in Fitting, enter the value of the allowed number of lines to be applied.

The value consists of four numbers, e.g.

2,1,0,0 

•The 1st value is the variation of the top edge - how many vertical nudges (VGs) it may go up;

•The 2nd value is the variation of the top edge - how many VGs it may go down;

•The 3rd value is the variation of the bottom edge - how many VGs it may go up;

•The 4th value is the variation of the bottom edge - how many VGs it may go down.

In the previous example, you allowed that the top edge of the frame can go for 2 vertical nudges, becoming effectively longer for 2 lines, and it can do down for 1 vertical nudge, becoming effectively shorter for 1 line.

To disable the frames resizing on all frames, on the Preferences dialog box, untick Scale Frames for Fitting.