I want to know how can I unblock or edit every HMI symbol library in Wincc.For example unblock a complicated tank and delete part of it and save it as a new symbol.
The HMI symbol library objects are ActiveX controls and so you cannot do much to alter there appearance and have them remain ActiveX controls.
However one way to modify the appearance is to export the control to an .EMF file (File\Export) and then import it back into the Graphics Designer. This will bring back the object but have broken it down into it's constituent parts. You can then modify the appearance by adding / deleting / changing the part you need, select the whole image and make it into a grouped or customised object.
One point to note, if you want the object to change colour and want to use the shaded colour options that the HMI symbol library offers, remember that once you've exported and imported the object it's no longer going to have the same configuration dialog box - so no shading option. To work around this, I set the colour of the object, export it to an .EMF, set the colour of the object again to the second colour, export it to a second .EMF, and then use the Status Display object to display the corresponding graphic depending on the state of the tag.
I hope this helps,