all items inside the effects toolbar item disappear when the items are not automatically generated and you tap on the effect toolbar again:
Example:
<telerikImageEditor:RadImageEditorToolbar Grid.Row="1"
ImageEditor="{x:Reference imageEditor}"
AutoGenerateItems="False"
IsMultiLine="True">
<telerikImageEditor:EffectsToolbarItem AutoGenerateItems="False">
<telerikImageEditor:ContrastToolbarItem AutoGenerateItems="False">
<telerikImageEditor:CancelToolbarItem HorizontalOptions="Start" />
<telerikImageEditor:TemplateToolbarItem>
<telerikImageEditor:TemplateToolbarItem.Template>
<DataTemplate>
<Slider Maximum="2" Minimum="0" Value="{Binding Value}" />
</DataTemplate>
</telerikImageEditor:TemplateToolbarItem.Template>
</telerikImageEditor:TemplateToolbarItem>
<telerikImageEditor:ApplyToolbarItem HorizontalOptions="End" />
</telerikImageEditor:ContrastToolbarItem>
</telerikImageEditor:EffectsToolbarItem>
</telerikImageEditor:RadImageEditorToolbar>