On a machine with an internet connection, double click the VSIX file.
The online machine will install the certificate to the local machine. After the VSIX installer opens, click the Digital Signature link to view more information about the certificate. Click Install Certificate.
Next, you'll want to export the certificate to a file. Use certmgr.msc to export the certificate.
Ensure you export all the certificates in the certificate path.
Move the P7B file to the offline machine along with the PowerShell Tools VSIX file. Install the certificate to the certificate store.
After creating the offline installation layout, you can then move the vslayout folder to an offline location. Within the certificates folder within vslayout folder, you may need to install all the certificates in order to correctly install the package.
Run the offline installation using the following command line.