I am using QGIS. On my maps, I have SVG Parking symbols. I need to use callouts to move them away. I have also a reference number beside many of these icons, but not all. How best to set this up? I tried this and it almost works... In the layer styling background tab, I added my SVG symbol. Created a field column for my reference #s and it displays. The original location marker point I do not need to see, so I disable the symbol layer. What I cannot solve is how to display the icon when there is no reference # in the field table, just NULL? Since it needs to see text in that field to display the background parking symbol, how do I find a workaround? Is there a trick or is my approach wrong?  To elaborate more on this issue, here are some screen caps. My Parking Icon with the reference number beside it as a callout. I like this no problems.  Here are my setting in the Background tab. I display the blue square P marker using the Background tab becouse I do not know how else to get the callout feature to work.  In the main Symbology window I turn off the layer that would show a marker at the original point. I do not what this to show as I will be scaling the maps and all those markers would colide on my rendered maps.  Lastly here is my Parking data table with my PLot column that I added. Note how fid 156 displays P4 because there is the number 4 in the field. But row 293 does not display P becouse there is no number in the field. (And I do not want one associated with that marker.) Yet I do what it to show up just as a P marker with no number beside it. How?
In QGIS, I have been learning a few expressions to style my trail maps but still know little and am stumped on what to use to filter my symbol data. I am showing Parking locations on my map. I use a marker symbol as a background element, so I can do callouts. I created a data field and added values to display beside this symbol a number that references a list of parking addresses in the book's text. All good except if the field has no number to display, it is NULL, it does not display my marker symbol. I need to filter this, so it does show even when there is no value in the field.
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