In JOSM it seems like it’s possible to see only objects at certain level (not sure if it is because of plugin or not), but that filter cannot allow me to choose only displaying objects that have no level tags. How to change it?
Also, is it just me that the level filter does not support filtering non-integral levels?
You could use a self-written filter for this. See the documentation for JOSM’s filter tool. You may want to do that anyway, as the built-in level selector is relatively limited. For example, it doesn’t work with multi-level features such as stairs running between levels, elevator shafts, or multi-level rooms.
There isn’t really any widely used tagging standard for non-integral levels at the moment. Simple Indoor Tagging, and similar conventions, tend to require integer levels. So many tools are likely to also assume integer levels.
I see, thanks