Class not found ProjectStructureDetector, while importing modules... (a feature under dev)

As per subject. I have tried to reinstall IntelliJ Platform SDK, but always this same same version is started. Short of removing all from Toolbox folder, no idea how to even try to change it. Documentation says IDEA-U dictates which version will be instantiated in sandbox... I have 2020.1.

Any suggestions?

2020-04-30 01:05:09,782 [  72916]  ERROR - nsions.impl.ExtensionPointImpl - While loading class org.m3w.intellij.ui.Modula3ProjectStructureDetector: com/intellij/ide/util/projectWizard/importSources/ProjectStructureDetector [Plugin: org.m3w.intellij-m3] 
com.intellij.diagnostic.PluginException: While loading class org.m3w.intellij.ui.Modula3ProjectStructureDetector: com/intellij/ide/util/projectWizard/importSources/ProjectStructureDetector [Plugin: org.m3w.intellij-m3]
	at com.intellij.ide.plugins.cl.PluginClassLoader.loadClassInsideSelf(PluginClassLoader.java:262)
	at com.intellij.ide.plugins.cl.PluginClassLoader.tryLoadingClass(PluginClassLoader.java:205)
	at com.intellij.ide.plugins.cl.PluginClassLoader.loadClass(PluginClassLoader.java:113)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
	at java.base/java.lang.Class.forName0(Native Method)
...
Caused by: java.lang.NoClassDefFoundError: com/intellij/ide/util/projectWizard/importSources/ProjectStructureDetector
	at java.base/java.lang.ClassLoader.defineClass1(Native Method)
	at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016)
	at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:877)
	at com.intellij.util.lang.UrlClassLoader._defineClass(UrlClassLoader.java:380)
	at com.intellij.util.lang.UrlClassLoader.defineClass(UrlClassLoader.java:376)
	at com.intellij.util.lang.UrlClassLoader._findClass(UrlClassLoader.java:340)
	at com.intellij.ide.plugins.cl.PluginClassLoader.loadClassInsideSelf(PluginClassLoader.java:259)
	... 88 more
Caused by: java.lang.ClassNotFoundException: com.intellij.ide.util.projectWizard.importSources.ProjectStructureDetector PluginClassLoader[org.m3w.intellij-m3, 1.0-SNAPSHOT] com.intellij.ide.plugins.cl.PluginClassLoader@fa982bf
	at com.intellij.ide.plugins.cl.PluginClassLoader.loadClass(PluginClassLoader.java:115)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
	... 95 more
2020-04-30 01:05:09,787 [  72921]  ERROR - nsions.impl.ExtensionPointImpl - IntelliJ IDEA 2020.1  Build #IC-201.6668.121 
2020-04-30 01:05:09,787 [  72921]  ERROR - nsions.impl.ExtensionPointImpl - JDK: 11.0.6; VM: OpenJDK 64-Bit Server VM; Vendor: JetBrains s.r.o 
2020-04-30 01:05:09,787 [  72921]  ERROR - nsions.impl.ExtensionPointImpl - OS: Linux 
2020-04-30 01:05:09,787 [  72921]  ERROR - nsions.impl.ExtensionPointImpl - Plugin to blame: Modula3 IDE support version: 1.0-SNAPSHOT 
2020-04-30 01:05:09,787 [  72921]  ERROR - nsions.impl.ExtensionPointImpl - Last Action: ImportModule