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Add custom repository by clicking the gear icon > Manage Plugin Repositories.
Add following repository URLs:
https://plugins.jetbrains.com/plugins/pricefx-eap/list (Jetbrains marketplace, 1-2 days delayprefered)
https://developer.pricefx.eu/studio/eap/ (hosted internally, will probably be closed in the future; no delay though)
Click OK.
Continue with step 3 in the previous section.
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