Nazi insignias are not forbidden in general, but for promoting the ideology.
Again the link to the resource:
https://en.wikipedia.org/wiki/Strafg...ch_section_86a
We actually have a Nazi party in Germany and they are free to express their opinions.
https://de.wikipedia.org/wiki/Nation...i_Deutschlands
https://en.wikipedia.org/wiki/Nation...rty_of_Germany
Some even vote for them and they have a few 'politicians' in communal and even state parliaments.
There have been several attempts to ban the party - one is still to be voted for by our Federal Constitutional Court.