Hi,
For the first problem, you need to change the code:
$this->rebuildTree();
to:
$this->importRebuildTree();
on the line of the error in administrator/components/com_hikashop/helpers/import.php
For the onDisplay error when editing categories and products, it comes from the fact that your wysiwyg editor does not implement all the functions it should. Please use another editor with the corresponding option in the configuration of HikaShop.
For the vm_redirect issue, it's a problem in the vm_redirect plugin. You need to add the line:
if(!include_once(rtrim(JPATH_ADMINISTRATOR,DS).DS.'components'.DS.'com_hikashop'.DS.'helpers'.DS.'helper.php')) return true;
just before the code:
$query='SHOW TABLES LIKE '.$db->Quote($db->getPrefix().substr(hikashop_table('vm_prod'),3));
in the file plugins/system/vm_redirect.php
and that will solve the problem.
For manufacturers: indeed, they are not imported for now. The manufacturer feature of HikaShop has been add only recently to HikaShop so we didn't had the time yet to add that to the import. We'll see what we can do this week to add that possibility.