Hello Lowell76,  The tips present in ProjectLibre is a tutorial that explains the main features of the software. A related tip the Baseline is this: It is always a good practice to save a baseline for your project. The ProjectLibre lets you save up to 11 baselines which can be shown in the Gantt chart and used for Analysis of Value Added. Conceptually a baseline is a photo of your planning. To save a baseline visit the Project Guide - Save Baseline. After performing this operation enter the columns related to the number of baseline. To insert a column right click on a column - Insert Column. We cost fields of the baseline and other information that may help you during the planning of their projects. I hope i help.

Would maybe suggest a feature which is "annotate" baselines. 
this helps us keeping track on what's changed. Or facilitate Change Configuration which tells us why a new baseline is created or altered.

That is a good suggestion! 

Is there any easy way to report on slippages against baseline, or show the differences between one baseline and another, in ProjectLibre?

I can insert filed like  "Baseline duration" / "Basleine 1 duration" into a GANTT and cut & paste them into Excel & produce reports from there, but it's all rather clumsy

Yes, you can do a baseline and then change the project and save Baseline 1-10   You can insert a column in the spreadsheet with various Baseline measures for the different baselines saved