I'm putting together the LEGO Orchid from the botanicals collection. On page 26 of the instruction booklet, step 34 has a strange icon: a white 2x2 brick with a "+" (plus) symbol.
There are no bricks that look anything like this piece being used in this step, and the arrow is pointing to a rod.
What is this icon trying to communicate?
It means that the part does not come in a numbered bag.
For example, see page 117 of the instructions for set 42158 "NASA Perseverance Rover", which I recently built:
That's telling me to get ready the contents of numbered bag 3, plus the wheels. If I recall correctly, the wheels did not come in any numbered bag, but rather in either an unnumbered bag or loose in the set's cardboard box.
Then the symbol is used again in the specific instructions step in which the aforementioned parts (in my case, the wheels) are used:
The same happens with bag 4 and some flex tubes. Again, the flex tubes were not inside bag 4:
This symbol is not only used in Technic builds. For example, see the instructions for set 60335 "Train Station":
Specifically for set 10311 "Orchid", note that the symbol also appears on page 20 of its instructions booklet, about what numbered bag goes next:
