I recall having a label-toggle button in the toolbar in earlier QGIS (2.x). If the selected layer had labels configured, then clicking this button would toggle their visibility off or on. The labels' formatting, placement etc would remain unchanged.. they'd just go visible or invisible. It was very useful functionality, particularly when I had to zoom out of one area and move to another. I'd toggle the labels off when I didn't need them - it also sped up the tool's response time. Can't figure out how to get that button again in QGIS 3. I can't remember if it was some specific plugin that did it, and now can't find any such plugin.
What do I need to do to get the toggle labels button back?
EDIT: Same question asked and answered here: Pause Labeling in QGIS?