Adding macros in ParaView is very easy. Just to to Macros > Add new macro... and select the file (ending with .py). Under Linux the macros will be stored under $HOME/.config/ParaView/Macros.

Clickable legend limit adjustment

This set of macros changes the legend limits per click and saves you the anoying typing of the legend levels again and again. L- and L+ decrease and increase the lower level respectively. H- and H+ do the same with the upper level. The increment is 5% of the current range. The corresponding data set must be selected in the pipeline browser.
Tested with PV 5.2.

Visualization of probe positions

This macro will read the controlDict and visualise the probe locations. The probes will appear as points in the pipeline browser.
Make sure you start ParaView in the OpenFOAM case folder!
Tested with PV 5.2.

Single click opacity change

These macros change the opacity of the selected object to 0.3 or 1. The single click is much faster then scrolling down and adjusting the value.
Wanted: The click on this macro should cycle the opacity value between 33%, 66% and 100%.
Tested with PV 5.2.

Animations from VTKs

The way OpenFOAM saves VTK files during a simulation is not directly compatible with ParaView. This tool creates soft links to the VTKs so ParaView can recognize them as time dependent data. The original files are preserved. The tool is practical for creating animations.