Problem exporting shape of flexible Grid with Quickplot - Forum - Delft3D

Hello everyone,
as the  new Delft3Dfm Forum prevents me from creating new posts, I post my Question here...hope that is ok.
I created a flexible mesh _net.nc file using the 2019 version of Delft3D FM. I would like to project my grid with a Program like ArcGIS together with other spatial data relevant. There is the possibility using Quickplot to export ArcView shapes wich works fine with rectangular .grd files created with Delft 3D but for some reason I am unable to do so with the flexible mesh. I also tried using the OpenEarthToolbox with MATLAB, again opening Quickplot and exporting a shape but it returns the error "unknown variable "fv" " which is burried in the codes behind quickplot exporter.
Any idea how to fix that problem? I am not bound to use Quickplot, if there is a way to convert my _net.nc (also have a _map.nc) into a polygon-shape of some sort and not just xyz-points.
Maybe there is a OpenEarthToolbox function I am not aware of.
Thank you in advance,
Karoline