I'm attempting to test out the forms in widgets and the block is not appearing in the block manager for me to choose it. Weirdly, it appears in the list when creating a custom block from a plugin.
System logs threw this up:
Template store key: template_21_cf26a6e403c332934cdd22fea1e7c649_widgets missing (form, front, widgets)
#0 /var/www/html/r266536/system/Theme/Theme.php(785): IPS\_Log::log('Template store ...', 'template_store_...')
#1 /var/www/html/r266536/system/Widget/Widget.php(122): IPS\_Theme->getTemplate('widgets', 'form', 'front')
#2 /var/www/html/r266536/applications/form/widgets/formForm.php(44): IPS\_Widget->init()
#3 /var/www/html/r266536/system/Widget/Widget.php(103): IPS\form\widgets\_formForm->init()
#4 /var/www/html/r266536/system/Widget/Widget.php(295): IPS\_Widget->__construct('59910d600a2a6', Array, '["sidebar","cms...', NULL)
#5 /var/www/html/r266536/applications/core/modules/front/system/widgets.php(71): IPS\_Widget::load(Object(IPS\form\Application), 'formForm', '59910d600a2a6', Array, '["sidebar","cms...', NULL)
#6 /var/www/html/r266536/system/Dispatcher/Controller.php(85): IPS\core\modules\front\system\_widgets->getBlockList()
#7 /var/www/html/r266536/applications/core/modules/front/system/widgets.php(38): IPS\Dispatcher\_Controller->execute()
#8 /var/www/html/r266536/system/Dispatcher/Dispatcher.php(146): IPS\core\modules\front\system\_widgets->execute()
#9 /var/www/html/r266536/index.php(12): IPS\_Dispatcher->run()
#10 {main}